any advice appreciated

I hope this is the correct subreddit for this, but I'm starting to think I'm a doormat or too nice. I still talk to the people who may have taken advantage of me in the past and when I think about it, I feel bad. The other part of me thinks I should be understanding and not hold on to negative emotions and stop thinking of my own friends like that. I'm kind of looking for insight on how to handle these situations or what I could have done differently.

-A friend of mine asked to borrow a DVD of mine years ago. I kind of hesitated and said it's my favorite movie and he said, "fine, don't lend it to me". I felt bad for saying that so I lent it to him and I never received it back. I kept reminding him afterwards, but he said he had to look for it and made excuses like saying he forgot. I stopped bothering him about it, but I met up with him a year later and asked him to bring said DVD before meeting up. Well he didn't, made more excuses. I'm meeting up with him next weekend, should I remind him to bring it or should I just forget about it? What do normal people do in these situations? I feel it's partially my fault because he initially said fine, forget about it and I lent it to him anyways. This happened many years ago and I doubt I'm going to get my movie back.

-Another friend I have hasn't always been the greatest friend, but I really like her. We used to live close to each other. One night we wanted to watch a movie and she said instead of getting pay-per-view, we should buy a movie together at a used music/CD shop and take turns keeping it. We each paid our half and watched the movie together, but I never saw that movie again. My sister told me that what I did was stupid, you don't purchase things like that with a person if you don't live together. I don't think we paid a lot for the movie, but I now realize that was dumb on my part. This same person also has borrowed things of mine and not returned them. I think I need to stop lending people stuff.

-Another time a friend from out of town came to my city for a couple weeks for some sort of yoga training seminar (she teaches it in a small town). I guess my place was perfect as it was only 10 min walk away from where class was. Sometime after she got settled in, she posted on Facebook that she was in the city for the week. One of our mutual friends (mutual friend that was really close to me in HS and the 3 of us have hung out together) commented on status "where in the city are you staying?" My friend answered with the name of area instead of saying she was staying with me. Like I said, we all know each other. Anyway I thought that was kind of funny, thought maybe she was embarrassed to be staying at my place or to be spending time with me, felt weird about it. The funny thing is I made lots of food, cleaned like crazy before she came and bought new towels and other stuff to make my place nice, nothing to do with her but this just shows how much I care which probably isn't good for me. I guess one of the people in her training seminar was nice enough to print her some stuff since she didn't have access to a printer and my friend bought her a nice dinner as a thank you. I thought that was nice of her, but she stayed at my place for almost two weeks. I don't expect her to treat me as I was doing a nice thing for her but it made me wonder if I'm actually her friend or if I was just being used. Why would she buy this person who printed stuff dinner anyway? I feel guilty for even thinking like that as I shouldn't do favors expecting anything back.

Anyway, I encounter these kinds of scenarios pretty frequently. I resent it sometimes. Since I've been lurking here for a couple days, I want to learn from my mistakes. Any input would be appreciated. Thank you

**Also I'm the type of person to offer to pay for people things because I want them to like me and I let people make fun of me. I know I don't speak up because I don't like fighting and conflict)